Varnishes based on natural resins have been used since ancient times to produce solid transparent or semitransparent coatings with protective and/or decorative properties. Among the natural resins, rosin has found widespread use in varnishes because of its inherent properties such as water repellency, abrasion resistance, adhesiveness, film formation, and integrity, which it imparts to coatings.
Rosin and its derivatives are particularly attractive for use in varnishes applied to humans and animals based on a historical safety profile. They have a long history as additives in chewing gum and personal care products. They are used as direct additives in foods and inactive ingredients in topical and oral pharmaceuticals. Rosin-based varnishes are useful when a removable, water-insoluble coating with good adhesion to human or animal tissue is required. They are particularly attractive when the varnish may be ingested or otherwise enter the body.
Because of their ease of application and excellent coating properties, varnishes are useful in dental applications. A dental varnish may act as a barrier alone or it may additionally contain a therapeutic agent or other additive for oral delivery. Currently, most dental varnishes are spirit varnishes, wherein a film forming, water-insoluble resin or polymer (natural or synthetic) is dissolved in a pharmaceutically acceptable solvent and applied to the desired tooth area. Varnishes that are most desirable do not require thorough drying of the teeth before application. The solvent evaporates and/or is extracted by saliva to leave a coating that remains on the tooth surface for a period of time, preferably at least several hours, though in practice, the actual time is often greatly reduced due to removal by the tongue and other mechanical removal.
Commercial dental varnishes are well known in the art. The first dental varnishes, used to coat prepared cavity walls prior to placement of restorative materials, were based on natural copal resins dissolved in chlorinated hydrocarbons and are still used to prevent penetration of restorative materials into dental tissue.
Particularly useful dental varnishes contain fluoride, which are usually administered to patients who are at high risk for dental carries. Fluoride varnishes are approved by the FDA as medical therapeutic for use as cavity preparation liners and for the treatment of hypersensitive teeth.
Despite the numerous benefits of dental varnishes, they still have limited use on dental patients compared to fluoride gels, foams, and rinses. An important disadvantage of traditional sodium fluoride varnishes based on natural resins is that the yellow to brown color of the natural resin causes a temporary change in tooth color. This undesirable characteristic limits patient acceptance of these natural resin varnishes and has promoted efforts to make varnishes based on modified natural resins in more acceptable lighter colors to increase patient acceptance.
Modified rosins that have been esterified and/or hydrogenated are available commercially in certain light colors. These modified rosins can produce a near colorless varnish. Unfortunately, compared to natural rosin, these materials have significantly lower solubility in solvents that are pharmaceutically acceptable for oral use. Ideally, solvents used in preparations that enter the body have acceptable taste, irritation, toxicity, and allergic reaction (sensitization) profiles. The most commonly used solvents in oral preparations requiring water miscibility are ethanol, glycerin, propylene glycol, and PEG 300 & 400. Applications for water immiscible solvents most often use liquid paraffin and vegetable oils. For topical use, saturated aliphatic hydrocarbons, ether, and isopropanol, among others, are also acceptable solvents.
Although a dental varnish is topical in its application, its prolonged residence in the oral cavity results in unavoidable and unintended ingestion, particularly the portion of the solvent that does not evaporate during the initial application. The ideal solvent, therefore, is low in toxicity, volatile enough to allow rapid drying of the varnish, water soluble, and extractable by bodily fluids, such as saliva. Since ethanol possesses these properties, it is a preferred solvent for applications where the varnish may enter the body, such as dental varnishes.
In certain varnishes, natural resins are replaced by certain food grade shellacs. Both the shellac-based and resin-based varnishes have shown to have similar efficacy when using fluoride at 5% and 2.5% sodium fluoride concentrations. However, these shellac-based products still possess certain limitations, including solubility, taste, and other performance limitations, which have limited their global use.
Generally, however, oral varnishes show great efficacy for reducing sensitivity, and off label use for remineralization in patients of all ages, including among children under 6, between 6-18 years, and adult populations is widespread. Yet, the several drawbacks to these products have reduced or minimized the use of these products, in what should otherwise be much more frequent use.
Accordingly, herein are described the creation of new products to create safe, reliable, and highly efficacious oral varnish products for application to tooth and oral mucosal surfaces, where the oral varnish includes therapeutic and other excipients that can repair or reduce caries, and otherwise treat oral tooth and mucosal surfaces.